8,780 research outputs found
A vertical monolithic combination of an InGaAsP/InP laser and a heterojunction bipolar transistor
A DH InGaAsP/InP mesa laser and a DH InGaAsP/InP mass-transport laser were successfully put together with an InGaAsP/InP heterojunction bipolar transistor in a vertical configuration. A laser threshold current as low as 17 mA and an output laser power of over 30 mW were achieved. Base injection current-controlled optical bistability and optical switching were demonstrated
Solar modulation of cosmic ray intensity and solar flare events inferred from (14)C contents in dated tree rings
The delta 14C values in 42 rings of a white spruce grown in Mackenzie Delta was measured as a continuing effort of tracing the history of solar modulation of cosmic ray intensity. The delta 14C values in six rings were measured, in search of a 14C increase due to two large solar flares that occurred in 1942. The results are presented
Illusion optics: The optical transformation of an object into another object
We propose to use transformation optics to generate a general illusion such
that an arbitrary object appears to be like some other object of our choice.
This is achieved by using a remote device that transforms the scattered light
outside a virtual boundary into that of the object chosen for the illusion,
regardless of the profile of the incident wave. This type of illusion device
also enables people to see through walls. Our work extends the concept of
cloaking as a special form of illusion to the wider realm of illusion optics.Comment: Including a paper and its auxiliary materia
Fragmentation and OB Star Formation in High-Mass Molecular Hub-Filament System
Filamentary structures are ubiquitously seen in the interstellar medium. The
concentrated molecular mass in the filaments allows fragmentation to occur in a
shorter timescale than the timescale of the global collapse. Such hierarchical
fragmentation may further assist the dissipation of excessive angular momentum.
It is crucial to resolve the morphology and the internal velocity structures of
the molecular filaments observationally.
We perform 0".5-2".5 angular resolution interferometric observations toward
the nearly face-on OB cluster forming region G33.92+0.11. Observations of
various spectral lines as well as the millimeter dust continuum emission,
consistently trace several 1 pc scale, clumpy molecular arms. Some of the
molecular arms geometrically merge to an inner
3.0\,, 0.6
pc scale central molecular clump, and may directly channel the molecular gas to
the warm (50 K) molecular gas immediately surrounding the centrally
embedded OB stars. The NH spectra suggest a medium turbulence line width
of FWHM2\,km\,s in the central molecular clump, implying a
10 times larger molecular mass than the virial mass. Feedbacks from
shocks and the centrally embedded OB stars and localized (proto)stellar
clusters, likely play a key role in the heating of molecular gas and could lead
to the observed chemical stratification. Although (proto)stellar feedbacks are
already present, G33.92+0.11 chemically appears to be at an early evolutionary
stage given by the low abundance limit of SO observed in this region.Comment: 37 pages, 23 figure
Effects of states and bottom meson loops on transitions
We study the dipion transitions . In particular, we consider the effects of the two
intermediate bottomoniumlike exotic states and as
well as bottom meson loops. The strong pion-pion final-state interactions,
especially including channel coupling to in the -wave, are taken
into account model-independently by using dispersion theory. Based on a
nonrelativistic effective field theory we find that the contribution from the
bottom meson loops is comparable to those from the chiral contact terms and the
-exchange terms. For the decay, the result shows that including the effects of the
-exchange and the bottom meson loops can naturally reproduce the two-hump
behavior of the mass spectra. Future angular distribution data are
decisive for the identification of different production mechanisms. For the
decay, we show that there is
a narrow dip around 1 GeV in the invariant mass distribution, caused
by the final-state interactions. The distribution is clearly different from
that in similar transitions from lower states, and needs to be
verified by future data with high statistics. Also we predict the decay width
and the dikaon mass distribution of the process.Comment: 25 pages, 8 figures, predictions of the decay width and the dikaon
mass distribution of the
process added, more discussions adde
Biomimetic coating of apatite/collagen composite on poly L-lactic acid facilitates cell seeding
Collagen and apatite were co-precipitated as a composite coating on poly L-lactic acid (PLLA) in an accelerated biomimetic process. The coating formed on PLLA films after 24 hours incubation was characterized. Saos-2 osteoblast-like cells were used to evaluate the cell seeding on this biomimetic composite coating. It was shown that cell seeding on PLLA films with the composite coating was greatly improved. PLLA coated with submicron collagen fibrils and submicron apatite paticulates can facilitate bone tissue engineering. ©2005 IEEE.published_or_final_versio
Strong decays of as a fully open-flavor tetraquark state
We have studied the strong decay properties of the recently observed
by considering it as a
fully open-flavor tetraquark state with
. In the framework of QCD sum rules, we have calculated the
three-point correlation functions of the two-body strong decay processes
,
and . The full width of is
obtained as MeV, which is consistent with the experimental
observation. We predict the relative branching ratios as , implying that the main
decay modes of state are and
channels in our calculations. However, the -wave decay mode is
also comparable and important by including the uncertainties. To further
identify the nature of , we suggest confirming
them in the and final states, and measuring the above ratios in
future experiments.Comment: 9 pages, 7 figure
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